$D0B5/53429/SCPU+69: JiffyDOS-/Speed Switch Flag
+-------+--------------------------------------------------------+
| Bit 7 | JiffyDOS Switch Flag: 1 = Enabled |
| Bit 6 | Speed Switch Flag: 1 = 1 MHz |
+-------+--------------------------------------------------------+
This register is read only with hardware registers enabled or
disabled (write with hardware registers enabled has no effect).